Grinding machine



March 12, 1963 F. P. HEALY ETAL 3,080,686

GRINDING MACHINE Filed Dec. 8. 1960 F'IC3-I l2 Sheets-Sheet l INVENTORS FRANCIS I P. HEALY CHARLES C STEWART FREDERICK F- GROLL.

ATTORNEYS March 12, 1963 F. P. HEALY ETAL 3,080,686

GRINDING MACHINE Filed Dec. 8. 1960 12 Sheets-Sheet 2 March 1963 F. P. HEALY EI'AL 3,080,686

March 12, 1963 F P. HEALY EII'AL 3,080,686

GRINDING MACHINE March 12, 1963 F. P. HEALY ETAL 3,030,636

GRINDING MACHINE Filed Dec. 8. 1960 12 Sheets-Sheet 5 March 12, 1963 F. PQHEALY ETA]. 3,080,686

GRINDING MACHINE Filed Dec. 8. 1960 12 Sheets-Sheet '7 FIG I7 ll A f? FIG- I6 235 4 Z34 23% v I z 1 I Z5 230 z z :52? zz 7/! l7 l7 ZZZ --//I I m5! 220 Q2 1 zl i i Z30 2'54 i I l March 12, 1963 F. P. HEALY EI'AL 3,080,686

GRINDING MACHINE Filed Dec. 8. 1960 12 Sheets-Sheet 8 FIG.2I

March 12, 1963 F. P. HEALY ETAI.

GRINDING MACHINE 12 Sheets-Sheet 9 Filed Dec. 8. 1960 F. P. HEALY ET Al.

GRINDING MACHINE March 12, 1963 12 Sheets-Sheet 10 Filed Dec. 8. 1960 F'IC3-28 March 12, 1963 F. P. HEALY ET AL 3,030,686

' GRINDING MACHINE Filed Dec. 8. 1960 12 Sheets-Sheet 11 16-290 l z 7) J/ jzz March 12, 1963 F. P. HEALY ET AL GRINDING MACHINE 12 Sheets-Sheet 12 Filed Dec. 8. 1960 FlC3 29b pa sszeA 4 United States Patent Ofifice 3,089,686 Patented Mar. 12, 1963 3,080,686 GRINDING MACHINE Francis P. Healy and Charles C. Stewart, Springfield, and Frederick F. Groll, West Springfield, Mass, assignors to Universal American Corporation, a corporation of Delaware Filed Dec. 8, I966, Ser. No. 74,555 17 Claims. (CI. 511l03) This invention relates to a grinding machine and, more specifically, to a centerless grinder.

It is the general object of the invention to provide a machine of the aforesaid type which is particularly adapted for automatically controlled high speed mass production of identical workpieces, but which can quickly and easily be set up for operation upon workpieces of difierent size and shape; and which incorporates novel drive and control means for accomplishing the grinding cycles to enhance the speed of operation wtihout departing from precision; and which also includes a novel wheel dressing assembly, a new mechanism for feeding or loading and unloading the workpieces in timed operation with the grinding cycles, and a new compensating assembly to efiect automatic readjustment of the regulating wheel assembly after a dressing operation.

The drawings show a preferred embodiment of the invention and such embodiment will be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawings and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part ofi this specification being relied upon for that purpose.

Of the drawings:

FIG. 1 is a front elevational view of a grinding machine incorporating the several features of the present invention; FIG. 2 is a top plan view of the grinding machine;

FIG. 3 is a perspective view of the machine taken generally from the rear thereof;

FIG. 4 is an enlarged top plan view of the regulating wheel assembly;

FIG. 5 is a front elevational view of the regulating wheel assembly;

FIG. 6 is a side elevational view of the regulating wheel assembly but with parts thereof shown in vertical section to illustrate details, the plane of the sectional portion being indicated by the line 66 of FIG. 5;

FIG. 7 is a transverse sectional view of the regulating wheel assembly taken as indicated by the line 77 of FIG. 4;

FIG. 8 is a detail view taken as indicated by the line 33 of FIG. 4;

FIG. 9 is a detail sectional view taken as indicated by the line 99 of FIG. 5;

FIG. 10 is a further detail of the regulating wheel assembly taken as indicated by the line 1010 of FIG. 4; FIG. 11 is a rear perspective view of a portion of the regulating wheel assembly to illustrate the means for adjusting the regulating wheel toward and away from the grinding wheel. I FIG. 12 is a horizontal sectional view of the drive means for moving the regulating wheel assembly toward and away from the grinding wheel in a feed cycle;

FIG. 13 is a vertical sectional view of the means for moving the regulating wheel assembly toward and away from the grinding wheel in a feed cycle and showing the said assembly base in retracted position; FIG. 14 is a view similar to FIG. 13 but showing the regulating wheel assembly base at an intermediate position in its movement toward the grinding wheel;

FIG. 15 is similar to FIGS. 13 and 14 but shows the said base in the fully advanced position;

FIG. 16 is a vertical sectional view of the grinding wheel dresser assembly taken in a longitudinal plane as indicated by the line 16-16 of FIG. 17;

FIG. 17 is a horizontal sectional view of the said dresser assembly taken in more than one plane as indicated by the line I7l7 of FIG. 16;

FIG. 18 is a schematic perspective veiw of the wheel dressers;

FIG. 19 is a schematic plan view of the dressing tools in the position of FIG. 18;

FIG. 20 is a veiw similar to FIG. 18 showing the dresser tools in another position;

FIG. 21 is similar to FIG. 19 but shows the dresser tools in the position of FIG. 20;

FIG. 22 is a perspective view similar to FIGS. 18 and 20 but showing the dresser tools in still another position;

FIG. 23 is a schematic view similar to FIGS. 19 and 21 but showing the dresser tools in the position of FIG. 22;

FIG. 24 is a fragmentary rear perspective view of the machine illustrating mechanism for adjusting the grinding wheel housing and dresser assembly relative to the grinding wheel;

FIG. 25 is a rear elevation of a portion of the machine showing the compensator assembly which actuates the means for adjusting the positions of the regulating wheel assembly and dresser assembly to compensate for wear and dressing of the grinding wheel;

FIG. 26 is a front elevational view of the work feeding and unloading mechanism for the machine;

FIG. 27 is a side elevational view of the apparatu shown in FIG. 26 but with a portion thereof shown in vertical section as indicated by the line 2727 of FIG. 26;

FIG. 28 is a horizontal sectional view of the work feeding mechanism taken as indicated by the line 28-48 of FIG. 26; and

FIGS. 2% and 2% combined show the electrical control wiring diagramof the machine. v

THE GENERAL ARRANGEMENT The centerless grinding machine of this invention is a compact unitary structure made up of a plurality of as: s'emblies including a grinding wheel assembly indicated generally by the reference numeral 30 and a regulating wheel assembly 32. The grinding wheel and regulating wheel assemblies are mounted on a machine bed or table 34 which is elevated from the floor on suitable legs and which has a cabinet-like section 36. The grinding wheel assembly includes an abrasive grinding wheel G and the regulating wheel assembly includes a regulating wheel R which is preferably made of tool steel. The grinding; wheel and regulating wheel are each rotated in .a clockwise direction as viewed from the front in FIG.,1. v The centerless grinding machine of this invention is; particularly adapted to operate in accordance with the in-feed method. That is, a workpiece is placed upon a work rest 38 which is an element of the regulating wheel assembly, and the workpiece is engaged and rotated by the regulating wheel R while it is supported on the work rest. Then, the regulating wheel assembly is advanced toward the grinding wheel assembly to engage the rotating workpiece with the rotating grinding wheel. After the grinding operation has been completed, the regulating wheel assembly is retracted and the finished workpiece is removed. In accordance with the present invention novel means is provided to eifect the aforedescribed reciprocatory feed movement of the regulating wheel assembly, this means including a drive motor which is located within the cabinet 36 of the machine bed 34. This drive motor attends only to reciprocation of the regulating wheel assembly 32 and it is not used to rotate the regulating wheel R. A separate drive motor 40 is provided as a part of the assembly 32 to rotate the regulating while R, this motor being located above the table 34 and reciprocable with the other elements of the regulating wheel assembly. This regulating wheel assembly will be described in far greater detail hereinafter.

The grinding Wheel assembly 30, unlike the regulating wheel assembly, is not reciprocated on the machine bed 34. The grinding wheel is driven by a motor which is located below the machine table 34 within its cabinet 36, and it is not shown. However, the belt and pulley connection from the grinding wheel drive motor is shown in FIG. 3 at 42, this connection being made to the grinding wheel shaft 44 which is suitably journalled in a fixed mount 45 to extend forwardly therefrom. The grinding wheel G is secured to the front end of the shaft 44 and is partially covered by a guard plate 46 (FIG. 1). The guard plate 46 forms a part of a general housing 48 for the grinding wheel assembly and for a grinding wheel dresser assembly which is supported within the left-hand end of the said housing as viewed in FIG. 1. The dresser assembly will be described in some detail hereinafter, but it should be noted that the housing 48 is adapted to be moved in increments from left to right toward the grinding wheel to engage the dresser assembly with the grinding wheel.

In addition to the units or assemblies heretofore mentioned, the grinding machine includes control means, lubricating means and a coolant supply means adapted to spray a coolant on the workpiece and in the grinding throat area generally as each workpiece is being ground. The control means is electrical and includes a control panel 50 which stands rearwardly of the machine per se and above the said machine. The coolant supply system includes a coolant tank or reservoir 52 located at the side of the machine, and this system also includes the necessary tubing, pumps, etc., for circulating the coolant as desired. It is thought that invention is not involved in the coolant supply system and means or in the lubricating system for the machine and these elements have not been illustrated except as shown in FIG. 1.

T he Regulating Wheel Assembly The machine table or bed 34 has a transversely extending dovetail slide 54 (FIG. 11) secured thereto which is received in a corresponding slot provided in a block or base 56 upon which the regulating wheel assembly 32 is mounted. As will be described hereinafter, the block 56 is reciprocated on the dovetail slide 54 to move the regulating wheel assembly and thus the regulating wheel toward and away from the grinding wheel in a feeding and grinding operation. As is also shown in FIG. 11, the block 56 is provided with a longitudinally extending dovetail slide 58 on its top surface and this dovetail is received within a slot cut in the bottom surface of a casting indicated generally by the reference number 60. The casting 60 is generally L-shaped when viewed from the rear and it includes a substantially horizontal bottom plate 62 and a substantially vertical side plate 64. A generally rectangular vertical face plate 66 is secured to the front end of the casting 60 as by screws 68, 68 to reside in a transverse plane and it cooperates with the casting to support directly and indirectly the remaining elements of the regulating wheel assembly.

The casting 60, the face plate 66, the regulating wheel R and the drive motor 40 are adjusted longitudinally as a unit by movement of the said casting on the dovetail slide 58 provided on the top surface of the block 56. This adjustment is obtained by means of a lead screw 70 which is threaded into a nut 72 secured to and depending from the bottom plate 62 of the casting 60 within a recess 74 defined in the front end of the block 56. The lead screw 70 is rotatably supported in a bearing 76 secured to the front end of the said block 56 and the said lead screw extends forwardly therefrom below the face plate 66. A knurled hand grip 78 and a wrench receiving head are provided on the extending front end portion of the lead screw 70 for manual rotation thereof.

The remaining elements of the regulating wheel assembly include a longitudinally extending vertical support plate 82 (FIG. 7) which has a longitudinal dovetail 84 received within a complementary slot in the inner face of the side plate 64 of the casting 60. The support plate 82 supports a longitudinally extending vertical mounting plate 86 which receives the regulating Wheel drive motor 40 and the bearing block for the shaft of the regulating wheel R. Thus, it will be seen that the side plate 64 of the casting 60, the slidable support plate 82 and the mounting plate 86 are disposed in side-by-side relationship and extend longitudinally and vertically. As will be described, the mounting plate is adjustably secured to the support plate so that it can be tilted relative thereto and thereby tilt the regulating wheel as may be desired for the grinding operation.

The support plate 82 is slidably adjusted longitudinally of the side plate 64 by means of a hand wheel 88 which rotates a feed screw 90 (FIG. 6). The feed screw 90 is threaded into the rear end of the said support plate and it is rotatably supported on a bearing block 92 which is secured to the rear end of the side plate 64 and extends inwardly therefrom. While rotation of the forwardly projecting feed screw 70 adjusts the L-shaped casting and all of the elements supported thereon longitudinally or forwardly and rearwardly of the machine, rotation of the rear. wardly projecting feed screw 90 effects longitudinal adjustment of the support plate 82, mounting plate 86, drive motor 40 and the regulating wheel R longitudinally relative to the bracket 60. This rotation of the rearwardly projecting feed screw 90 by means of the hand wheel is accomplished for the purpose of projecting the regulating wheel R forwardly of the face plate 66 the amount desired or necessary to accommodate workpieces of known length.

An indicator 94 (FIG. 4) is preferably supported as by a bracket 96 on the side plate 64 of the casting 60 to provide an indication of the movement of the regulating wheel assembly with the casting relative to the block 56, this being to locate the regulating wheel assembly as a unit in a desired longitudinal position. As shown in FIG. 4, the stem 98 of the indicator 94 engages the end of a pin 100 which is supported as by a bracket 102 secured to and extending to the side from the rear end of the block 56 As mentioned above, the regulating wheel drive motor 40 is secured to the mounting plate 86. As shown in FIGS. 4, 5 and 6, the base 104 for the motor is vertically adjustably secured to the mounting plate 86 as by screws 106, 106 which are threaded into the mounting plate and extend through slots 108, 108 in the motor base 104. The vertical adjustment of the motor 40 relative to the mount ing plate 86 is accomplished rather critically by means of a jackscrew 110 which is threaded vertically into a bracket 112 secured to the top of the motor base 104 and which butts against the top surface of the mounting plate 86.

A pulley 114 is axially adjustably secured to the shaft of the drive motor 40, and a belt 116 extends from that pulley to a pulley 118 secured to the rear end of a shaft 120 which mounts the regulating wheel R at its front end. The shaft 120 is rotatably supported in suitable anti-friction bearing units within a bearing block 122 which is also mounted upon the mounting plate 86 as by cap screws 124, 124. The drive motor and the regulating wheel shaft support being secured to the mounting plate 86 as described and the mounting plate being supported by the support plate 82, it will be seen that by longitudinal adjustment of the said support plate the regulating wheel R can be projected as desired from the face plate 66.

As has been mentioned, the regulating wheel can be tilted as desired for the grinding operation, this tilting being accomplished by pivotally adjusting the mounting plate 86 relative to the support plate 82. The support plate is adapted for this purpose by providing it at its central dovetail section with a longitudinally forwardly projecting extension 126 (FIG. 4). The end of the forwardly projecting extension 126 on the support plate 82 is generally cylindrical and it is provided with a transverse horizontal bore 128 (FIG. 9). This bore receives the head 130 of an eyebolt having a threaded stem 132 which is loosely embraced by a bushing 134 and which extends through an unthreaded bore in an extension 136 on the mounting plate 86 similar to the extension 126 on the support plate 82. The extending threaded end of the eyebolt stem receives a nut 138 which is threaded to the eyebolt stem to engage the exposed vertical face of the mounting plate extension 136. The eyebolt has a tapered bore 140, and a binder screw 142 having an unthreaded tapered extension 144 is threaded longitudinally into the end of the support plate extension 126 so that its tapered portion will engage the similarly tapered but larger diameter bore 140 of the eyebolt 130.

It will be seen in FIG. 9 that if a suitable wrench is applied to the binder screw 142 to advance it into the support plate extension 126, its tapered portion will engage the taper on the eyebolt bore 140 and shift the eyebolt transversely to the right to apply a clamping force between the mounting plate 86 and the support plate 82. On the other hand, if the binder screw 142 is retracted relative to the support plate extension, the clamping force applied by the eyebolt 130 and nut 138 is released and the mounting plate 86 can be pivoted relative to the support plate 82 on the bushing 134 around the axis of the said bushing and eyebolt.

The said pivotal adjustment of the mounting plate relative to the support plate achieves the desired tilt adjustment of the regulating wheel R. In any event, the regulating wheel is to be tilted only a limited amount. The tilting is limited in this construction by relative movement of an additional clamping eyebolt 146 within an arcuate slot 148 in the mounting plate 86 (FIGS. 7 and 8). The slot 148 in the mounting plate 86 is spaced rearwardly from its pivot axis on the eyebolt 132, the arc of the slot 148 being struck from the said pivoted axis. Similarly to the first described eyebolt, the eyebolt 146 is disposed within a bore 150' provided in the support plate 82, and the eyebolt has a tapered bore 152 wh ch is adapted to receive a tapered unthreaded shank portion on a binder screw 154 which is threaded into the support plate 82 from the top thereof. A clamping dog 156 loosely embraces the threaded end of the eyebolt 1 46 and rests within the arcuate slot 148 so that by advancing and retracting the binder screw 154, clamping force Wlll respectively be applied and released through the clamping dog 156 to the mounting plate 86 and support plate 82.

When the operator desires to effect a tilt adjustment of the regulating wheel R, he merely loosens the front and top binder screws 142 and 154 and then pivotally adjusts the mounting plate 86 relative to the support plate 82 on the axis of the eyebolt 132 by supporting the welght of the drive motor 40 and the other members of the regulating wheel subassembly. The subassembly secured to the mounting plate 86 can easily be supported in adjusted positions by the operator holding the drive motor. When a desired tilted condition of the regulating wheel is achieved, the operator tightens the binder screws 142 and 154 to secure the said subassembly in adjusted position.

An adjusted tilted or pivoted position of the regulating wheel subassembly can be selected by reference to a degree scale 1'58 marked adjacent a longitudinal slot 160 provided in a metal plate 162 secured to the top of the support plate 82 so that its slot 160 overlies the mounting plate 86 (FIG. 4). A spring steel indicator or pointer 164 is secured to the top of the mounting plate 86 so that its front edge 166 is adjacent and below the scale slot 160. When pivotally adjusting the mounting plate 86 relative to the support plate 82, the said front edge 166 of the pointer 164 will be visible to the operator through the slot 160 and can be seen in registry with the scale 158 to indicate the angularly tilted position of the mounting plate, the scale being calibrated in degrees for this purpose.

The Means for Reciprocating the Regulating Wheel Assembly for ln-Feed Operation As mentioned earlier, the regulating wheel assembly block is movable transversely on the machine table or bed 34 over the dovetail slide 54 provided thereon. In accordance with the present invention, means are provided for transversely adjusting the position of the block 56, and thus the position of the entire regulating wheel assembly 32, on the machine bed 34 and dovetail slide 54 relative to the grinding wheel G and its assembly, and

means are provided for thereafter reciprocating the block and assembly along the slide 54 toward and away from the griding wheel G in the feed cycle or in-feed operation of the machine. The means for adjusting the position of the block 56 to an initial position include the hand wheel 168 secured at the right-hand front end of the machine to a longitudinally extending worm shaft 170 (FIG. 11). The said shaft extends to the rear of the machine and has a ratchet wheel 172 pinned thereto and it rotatably supports a gear segment 174. The ratchet wheel and gear segment are utilized in the compensator unit to rotate the worm shaft 170 as will be described hereinafter. At this time, manual rotation of the worm shaft 170 as by the hand wheel 168 is all that is being considered.

Intermediate its ends, the worm shaft 170 has a Worm 176 secured thereto and which engages a worm wheel 178 which is suitably rotatably supported in a journal box' 180 secured to the machine bed 34 on the right-hand side thereof. A gear 182 is coaxially aligned with the worm wheel 178 to rotate therewith, and the said gear meshes with another gear 184 which is secured to a feed screw 186. The said screw 186 extends transversely with its threaded end extending inwardly from the journal box 180 into the regulating wheel assembly block 56, and the feed screw has an outer end 188 which extends from the journal box 180 at the other side thereof and which'is provided with a wrench receiving head. Thus, the feed screw 186 can be rotated manually either by turning the hand-wheel 168 on the worm shaft 170 or by applying a wrench to the end 188 of the said feed screw.

Referring now to FIGS. 12-l5, it will be seen that the threaded end of the feed screw 186 extends into a transversely extending bore 190 in the block 56. The bore 190 is preferably rectangular in cross section and it receives aslide block 192 which projects into the bore from the right-hand end thereof. The inner end of the slide block 192 is bifurcated to define furcations 194, 194. These furcations support a longitudinally disposed pivot pin 196, the purpose of which will be described hereinafter. The slide block 192 is also provided with a bore extending from its right-hand end, and the feed screw 186 extends into this bore wherein it is threaded into an inner nut 198 and a spaced apart outer nut 200. The nut 208 is secured to the slide block 192 at its outer end to prevent it from turning and moving longitudinally in the bore of theslide block. The inner nut 198 is keyed to the slide block 192 to prevent it from turning but to permit longitudinal movement of it within the bore of the slide block. As previously mentioned, the feed screw 186 is threaded into both nuts, and a compression spring 202 is interposed between the said nuts and around the said feed screw to prevent backlash in the threaded engagement. Thus, when the feed screw 186 is rotated in either direction there will be instant response in movement of the nut 200 along the said feed screw.

The longitudinally extending pin supported in the bifurcated end of the slide block 192 pivotally receives one end of a pitman 204 which is pivotally connected at its other end to an accentric portion 206 of a driven shaft 288 which is rotatably supported in a longitudinally extending bore in the regulating wheel assembly block 56. The front end of the driven shaft 208 projects forwardly of the block 56 for a purpose that will be described hereinafter while the rear end of the shaft projects rearwardly of the block to secure a pulley 210 and a earn 212. The purpose of the cam will be described later, but the obvious purpose of the pulley is to receive a drive belt 214 (FIG. 11) extending from the drive motor (not shown) which is located within the cabinet section 36 of the machine frame.

When the driven shaft 208 is rotated by the said drive motor it reciprocates the block 56 on the dovetail slide 54 and relative to the slide block 192. That is, the eccentric portion 206 of the said shaft 208 being connected at one end to the pitman 204 while the other end of the pitman is connected to the bifurcated end of the slide block 192 as by the pin 196, the non-eccentric portions of the shaft 208 being rotatably journalled in the block 56. each revolution of the drive shaft 208 will cause a cycle of reciprocation of the block 56 and the regulating wheel assembly 32. FIGS. 13, 14 and 15 schematically illustrate progressive movement of the assembly block 56 from a retracted position wherein the regulating wheel is fixed the greatest distance from the grinding wheel to an advanced position wherein the regulating wheel comes closest to the grinding wheel in the grinding operation. As will be described hereinafter, means are provided to control the speed of the reciprocating drive motor and thus to control the speed of rotation of the driven shaft 208 so as to advance the regulating wheel toward the grinding wheel rapidly from its retracted position until it approaches its advanced grinding position, to then advance the regulating wheel with less speed during the grinding operation and then to rapidly retract the regulating wheel.

It will be understood from the foregoing description that the regulating wheel assembly is transversely adjusted to an initial position relative to the grinding wheel by rotation of the worm shaft 170, this causing rotation of the feed screw 186 which is indirectly connected with theslide block 192 to move it and the assembly base 56. This rotation of the worm shaft is effected manually at the hand wheel 168 or automatically by the compensator assembly as will be described. Thereafter the regulating wheel is reciprocated from the initial position toward and away from the grinding wheel in the feed and grinding cycle of the machine by rotation of the driven shaft 208 having the eccentric portion 206 which is indirectly connected to the slide block 192 to reciprocate the assembly base 56 relative to the said slide block.

The Grinding Wheel Dresser Assembly As previously mentioned, the dresser assembly for the grinding wheel is mounted in the left-hand end portion of the grinding wheel housing indicated generally by the reference numeral 48. As was also previously mentioned, the housing 48 is adapted to be moved transversely of the machine bed 34 from left to right or toward the grinding wheel. Thus, the dresser assembly may be advanced into operating position to dress the grinding wheel by engaging its periphery from the side of its axis opposite to the regulating wheel assembly.

The wheel dresser assembly as shown in FIG. 16 has an independent drive motor 220 which is mounted on the rear end of the grinding wheel guard housing 48 with its shaft extending horizontally and transversely of the machine. A pulley and belt connection indicated at 222 connects the motor with a worm shaft 224 having a worm 226 keyed thereto and engaging a worm gear 228 which is keyed to a vertical shaft 230 rotatably supported in the rear upper portion of the grinding wheel guard housing 48. A pulley 232 is keyed to the upper end of the driven vertical shaft 230, and a belt 234 extends from that pulley to a pulley 236 secured to the upper end portion of a main dresser shaft 238 which is vertically rotatably supported in the grinding wheel housing 48 so that its axis is in the same transverse plane with the grinding wheel G.

Gear teeth 240 are provided on the main vertical shaft 238 of the dresser assembly below the pulley 236 so that the said shaft provides a pinion rotatable on a vertical axis. The pinion thus defined is engaged by a front and by a rear gear segment 242 and 244 respectively keyed to the upper ends of a pair of shafts 246 and 248. The vertical shafts 246 and 248 are rotatably supported in the grinding housing 48, the shaft 246 being located forwardly of the main dresser shaft 238 and the shaft 248 being located rearwardly thereof. The shafts 246 and 248 are supported within the housing 48 as shown so that their bottom ends extend downwardly to receive dressing tool arms 250, 250 which are keyed to the respective shafts. The bottom end of the main dresser shaft 238 extends beyond the other shafts and is supported in the housing 48, but intermediate its ends the said main shaft secures a dressing tool holder 252. The dressing tool arms 250, 250 and the dressing tool holder 252 are arranged and constructed to hold diamond tip dressing tools 254, 254 so that the diamond tips thereof reside in substantially the same horizontal plane as the axis of the grinding wheel.

The dresser assembly drive motor 220 is a reversible electric motor and when operated to drive in one direction, it will rotate the shaft 238 counterclockwise as viewed from the top. When the shaft 238 is driven counterclockwise, it will rotate the gear segments 242 and 244 and the shafts 246 and 248 clockwise from the positions shown in FIG. 17. The positions of the gear segments and dressing tool shafts shown in FIG. 17 are the initial positions for these elements at the start of a dressing cycle. Control means are provided to limit the operation of the drive motor before reversal thereof so that the main dresser shaft 238 will rotate substantially 180 counterclockwise from the position shown, this causing substantially of clockwise movement of the gear segments 242 and 244 and of their dresser shafts 246 and 248, respectively.

When the drive motor 220 is reversed to cause clockwise rotation of the main dresser shaft 238, counterclockwise rotation of the shafts 246 and 248 will result until all elements return to the initial position as shown in FIG. 17.

This rotation of the dresser shafts swings the diamond tip dresser tools which they support through arcs as diagrammatically illustrated in FIGS. 18-23. FIGS. 18 and 19 show the dresser tools in their initial positions, FIGS. 20 and 21 show the tools in the positions occupied When the main dresser shaft has been rotated 90 counterclockwise, and FIGS. 22 and 23 show the dresser tools in the positions occupied when the main shaft 238 has been rotated 180 counterclockwise and is ready to start its return clockwise rotation to the initial position.

As is further illustrated by FIGS. 18-23, the dressing tool carried by the main shaft 238 is used to dress the edge of the grinding wheel G in a radius. The dressing tool carried by the front shaft 246 is arranged to dress the front peripheral portion of the grinding wheel so as to provide an arcuate cut or hollow ground edge. The dressing tool carried by the rear shaft 248 provides similar dressing of the rear face of the grinding wheel adjacent its periphery. Preferably, the tools carried by the shafts 246 and 248 are positioned to swing nearer to the axis of the shaft 238 than the diamond tip on the tool carried by the shaft 238. Therefore, the tip of the tool on the shaft 238 performing the radial dress will not engage the grinding wheel G at the initial position of the shaft 238 or 180 therefrom. Preferably, the diamond carried by the main dresser shaft dresses the radial edge through approximately It has been found that a wheel dressed as described performs the best grinding of the external groove in the internal race of a ball hearing workpiece.

While the dressing assembly is motor driven as described, and while the control means is preferably adapted to cause wheel dressing automatically after a selected number of workpieces have been ground, means are provided for manual rotation of the dresser shafts. The said means comprises a hand wheel 256 mounted on the outwardly extending end of the worm shaft 224 and provided with clutch teeth 258 which can be selectively engaged with similar teeth on a clutch element 260 keyed to the said worm shaft. Normally, the hand wheel 256 is biased out of clutch position by means of a spring 262 so that the hand wheel will not be rotated during power operation of the dresser assembly.

As has been mentioned, the grinding wheel housing 48 can be moved transversely on the machine bed 34. Such movement is accomplished along a dovetail slide 264 on the bed 34, the housing 48 being provided with a complementary dovetail slot. The housing 48 can be manually reciprocated on the slide by means of a hand wheel 266 keyed to a worm shaft 268 which is supported to eX- tend longitudinally at the left-hand side of the machine bed. A worm 270 is secured to the worm shaft within a journal box 272 and within the said box it engages a worm gear 274 secured to a feed screw 276. The feed screw is threaded into a suitable aperture in the lefthand end of the housing 48 so that rotation of the worm shaft 268 by the hand wheel 266 will cause sliding movement of the housing 48 over the slide 264. Obviously, this sliding movement can be in either transverse direction depending upon the direction of rotation of the hand wheel. The rear end of the worm shaft 268 has a ratchet wheel 278 secured thereto and a gear segment 280 is rotatably supported on the said worm shaft adjacent to but forwardly of the ratchet wheel 278. The said ratchet wheel and gear segment are elements of the compensating assembly which will now be described.

The Compensating Assembly The compensating assembly is used'to automatically advance the grinding wheel housing 48 and the dresser assembly carried thereby toward the grinding wheel to dress the grinding wheel, and it also adjusts the initial position of the regulating wheel assembly toward the grinding wheel to compensate for wear and dressing of the grinding wheel. The compensating assembly includes a reversible electric motor 282 (FIG. 25) located at the rear of the machine and which functions to drive a pinion 284 engaging a movable rack 286 which extends transversely of the machine. At one end, the rack engages the gear segment 174 which is rotatably mounted on the worm shaft 170 for moving the regulating wheel assembly, and at the other end the rack engages the gear segment 280 on the worm shaft 268 for the dresser assembly and grinding wheel housing 48.

In FIG. 25, the rack 286 is shown in its initial position from which it is moved in a compensating cycle. In said initial position a dog 288 carried by the rack engages a limit switch 2L8, and as will be described, this limit switch is a part of electrical control means for the motor 282. The control arrangement is such that when the motor 282 is energized the rack is moved from left to right as viewed in FIG. 25 until another dog 290 carried by the said rack engages and closes another limit switch 3L8. As will be described, this limit switch is used in reversing the direction of operation of the motor 282 and thus reversing the direction of travel of the rack 286.

When the motor 282 is energized to start a compensating cycle and the rack 286 is moved from left to right, the gear segments 174 and 280 on the worm shafts 170 and 268, respectively, are rotated in a clockwise direction. Each of these segments carries a pawl 292. The pawl on the gear segment 174- is arranged to engage and rotate the ratchet 172 when the gear segment 174 is rotated clockwise as described. However, when the segment 174 is rotated counterclockwise, the pawl 292 will not engage and rotate the ratchet wheel 172. Since the ratchet 172 is keyed to the worm shaft 170, the worm shaft is rotated with the ratchet as the rack is moved from left to right in the initial portion of the compensating cycle. This rotation of the worm shaft 170 advances the regulating wheel assembly toward the grinding wheel to compensate for the wear and dressing of the grinding wheel so that all workpieces handled will be ground to the same diameter. When the limit switch 3LS is engaged and the motor 282 is reversed and the rack 286 is returned from right to left to its initial position, the gear segment 174 is rotated counterclockwise, but this causes no rotation of the ratchet 172 and worm shaft 170. When the segment 174- has been returned to its initial position as shown in FIG. 25, the pawl 292 will engage an adjustable stop 294 which disengages the pawl from the ratchet 172 whereby the worm shaft and ratchet 172 can be manually rotated as previously described without causing any movement of the compensating rack 286.

Similarly, when the rack is moved from left to right in the initial part of the cycle, the pawl 292 carried by the gear segment 280 engages the ratchet 278 to rotate the worm shaft 268. This causes movement of the dresser assembly and grinding wheel housing 48 toward the grinding wheel. When the rack is moved from right to left in the latter part of its cycle, the pawl 292 on the segment 280 slips past the teeth of the ratchet 278 and does not rotate it. When thegear segment 280 has been returned to its initial position as shown in FIG. 25, its pawl 292 will engage an additional adjustable stop 296' to disengage the pawl from the ratchet and thereby to permit manual rotation of the dresser assembly worm shaft 268 without effecting movement of the compensating rack 286. 1

The control of the compensating assembly will be described hereinafter in connection with a general description of the machine control means and operation.

The Work Feeding Assembly As shown in FIG. 26, there is a work rest blade 298 supported on the regulating wheel face plate 66 by the work rest 38. In accordance with standard centerless grinding techniques, each workpiece is supported in turn by the upper edge of the work rest blade 298 and while so supported, the workpiece is ground. Each workpiece, which is identified by the letter W in FIG. 26, is moved from a work feeding magazine 300 above the face plate 66 into position on the work rest blade. A work guide 302 is resiliently pivotally supported above the blade 298 to help guide and support each workpiece in its move-v ment from the magazine onto the blade.

The workpieces illustrated are the ring-like inner races. for ball bearings, and it will be observed in FIG. 26 that these workpieces are stacked vertically within the magazine 390 so that the bottom workpiece W rests upon a stop 303 and can be removed therefrom. The means for removing the workpiece from the bottom of the stack at the magazine comprises an adjustable two-piece arm 384 which is rotatably and axially movably sup ported on a stub shaft 386 (FIG. 28) extending forwardly from and supported by the face plate 66. The arm 304 carries a pintle 388 which is provided with a reduced diameter end that can be inserted within the aperture of each workpiece W. As viewed in FIG. 26, the arm is in a substantially vertical position when it receives or picks up a workpiece at the magazine 308 and it is then pivoted counterclockwise to a substantially horizontal position when the workpiece has been delivered to and is supported on the top of the work rest blade 298. An adjustable stop 310 engages the arm 304 in the vertical position and an adjustable stop 312 engages it in the horizontal position.

The work feeding or loading and unloading mechanism is, in accordance with this invention, wholly mechanically operated by means operatively associated with the drive means which reciprocates the regulating wheel assembly toward and away from the grinding wheel. Therefore, the work loading and unloading operations are accomplished in timed relationship with the grinding operation.

In keeping with this, the work feed mechanism is driven off a shaft 314 (FIGS. 26 and 27) projecting from the front face of the regulating wheel assembly block 56 below the face plate 66. The shaft 314 is connected by motion transmitting means with the motor driven drive shaft 208 which reciprocates the regulating wheel assembly. The projecting front end portion of the shaft 314 extends into a box-like housing 316 which is mounted on the regulating wheel assembly base 56. A cam 318 is secured to the shaft 314 within the housing 316 to engage and pivot a cam follower 320 secured to a stub shaft 322 which projects forwardly of the housing 316. A crank arm 324 is keyed to the projecting front end of the stub shaft 322 and at its free end it is pivotally connected to the bottom end of an adjustable length connecting rod 326. The upper end of the connecting rod 326 is pivotally connected to the two-piece work loading and discharging arm 304.

The configurations and arrangements of the cam 318 and follower 320 on their respective shafts 314 and 322 are such as to pivot the work loading and discharging arm 304 downwardly from the magazine 300 to the work rest blade 298 while the regulating wheel assembly is spaced from the grinding wheel. Further, the configuration of the cam 318 is such as to retain the arm 304 against the stop 312 for the period of time it takes for the workpiece on the work rest blade to be engaged by the grinding wheel and fully ground. Further, the configuration and arrangement of the cam 318 is such as to permit the return of the work loading arm 304 to the vertical position after the grinding operation has been completed. The means returning the arm upwardly comprises a tension spring 328 having one end connected to the crank arm 324 and the other end connected to a pin 330 secured to the front face of the cam and shaft housing 316. This spring biases the crank arm 324 clockwise (FIG. 26) to pivot the loading arm 304 clockwise against the upper stop 310, and the loading arm can be returned to the lower stop 312 only by operation of the cam 318.

Obviously, some forward and rearward movement of the loading arm 304 and its pintle 308 must be provided for in order to have the pintle move into and out of the bore of each workpiece when picking it up and releasing it. It is also obvious that such fore and aft movement must be accomplished during the pivoting movement of the loading arm. The means effecting this fore and aft movement include a cam block 332 having a sloped cam surface 334 and which is pivotally connected to a plate 336 secured to the face plate 66. The c-am block 332 is biased in a counterclockwise direction by a spring 338 into engagement with a stop pin 340 projecting forwardly from the plate 336 (FIG. 26). That portion of the two-piece loading arm 304 which is rotatable about the stub shaft 306 is provided with two sloped follower surfaces 342 and 344 (FIG. 27).

The cam surface 334 and the follower surfaces 342 and 344 are arranged so that as the arm 304 is pivoted clockwise while being elevated, the sloped surface 342 will engage the cam surface 334 and thrust the loading arm 304 forwardly or outwardly with respect to the face plate 66. This forward thrusting movement of the arm 304 is opposed by a compression spring 346 (FIG. 28) which biases the arm 304 rearwardly or toward the face plate. The full extent of the forward movement of the loading arm 304 will be reached when the pintle 308 is over the upper end of a discharge chute 348 which is mounted on the face plate 66. Accordingly, as the arm 304 is moved upwardly and forwardly, a ground workpiece W can be slipped off the pintle 308. A suitable ejector or the like can be secured to the face plate 66 to engage the workpiece over the discharge chute 248 to assure that it is removed from the pintle.

In continuing the clockwise pivoting movement of the loader arm 304 beyond the position over the upper end of the chute 348, the sloped follower surface 344 will engage the sloped cam surface 334 permitting the arm 304 and its pintle 308 to move rearwardly or toward the face plate 66. The configurations and arrangements of the said follower surface and cam surface are such as to provide complete rearward movement of the arm 304 only when the said arm is in a substantially vertical position. This permits the reduced end portion of the pintle 308 to be moved into the bore of the lowermost workpiece W which rests against the stop 303.

Having received an unground workpiece at the magazine 300, the loading arm 304 is then ready to be pivoted downwardly or counterclockwise to position the said workpiece on the work rest blade 298 for grinding. When the arm 304 is pivoted counterclockwise by operation of the cam 318, the sloped follower surface 344 on the arm 304 will engage the flat back surface of the cam block 332 and pivot it clockwise against the force of the biasing spring 338. Thus, the cam 332 is thrust out of operating position and the arm 304 is not shifted forwardly as it is pivoted downwardly in the loading stroke. During such loading stroke of the arm 304, the unground workpiece will engage the resiliently pivotally supported work guide 302 which assists in directing it properly to the top of the work rest blade 298. During the grinding operation, the reduced end portion of the pintle 308 can remain within the bore of the workpiece being ground provided the said reduced end fits sufficiently loosely within the bore. If necessary, means generally similar to the cam means 332 can be employed to shift the arm 304 and pintle 308 forwardly for the duration of the grinding operation.

The Electrical Control and General Operation of he Machine In describing the electrical control and general operation of the machine, frequent reference will be made to the electrical diagram shown in two parts in FIGS. 29a and 2912. There are many elements shown for the first time in this diagram, and they are illustrated only schematically since they comprise conventional commercially available devices.

Assuming the grinding wheel G to be properly dressed and that the magazine 300 is loaded with workpieces to be ground, and assuming further that the regulating wheel assembly 32 is in its retracted or initial position, the operator should at first check and, if necessary, adjust the initial position of the regulating wheel assembly for the grinding of workpieces to a preselected diameter. That is, the amount of movement of the regulating wheel assembly and the regulating wheel toward the grinding wheel is a known constant. Therefore, the initial position of the regulating wheel assembly should be located so that the regulating wheel will be separated from the grinding wheel by the desired ground or finished diameter of the workpiece when the regulating wheel assembly has completed its forward stroke. The initial location of the regulating wheel assembly can be accurately selected by reference to a scale provided on the hand wheel 168 for the regulating wheel worm shaft 170, the said hand wheel being adjusted to effect the location of the regulating wheel assembly in the selected position.

Then, the step to be taken is to start operation of the grinding wheel. This is done by closing a biased open push button start switch 400 in an A.C. circuit which includes a grinding wheel motor relay IMR. This circuit includes a biased closed emergency stop switch 402 which can open all circuits hereinafter to be described, and it also includes a biased closed grinding wheel stop switch 404. The circuit extends between a conductor 406 and a conductor 408 which are connected to the lower side of a step-down transformer 410, the conductor 408 being indirectly connected thereto through a series of normally closed circuit breaker contacts which will be referred to hereinafter.

The said step-down transformer 410 preferably transforms 440 volt 60 cycle A.C. to volt 60 cycle A.C., the 440 volt leads L1 and L2 to the transformer being connected with a three-phase grinding wheel motor 412. The third or neutral lead to the grinding wheel motor is identified by the reference L3 and each lead to the grind ing wheel motor is provided with a set of normally open relay contacts 414 which will be closed when the motor relay lMR is energized whereby to energize the grinding wheel motor 412. It will be observed that the lead lines L1 and L3 to the grinding wheel motor each includes a thermal overload 416 which will operate to open one of a pair of circuit breakers 418, 418 in the motor relay circuit to deenergize the motor relay lMR and thus to deenergize the grinding wheel motor 412 in the even the said motor encounters an overload.

The wheel start switch 400 need not be held closed to sustain operation of the grinding wheel motor, because parallel interlock contacts 420 closed by the motor relay lMR are provided. The operator can ascertain when the relay lMR is energized by observing an amber lamp 422 connected in parallel with the said motor relay, and upon observing the lighted condition of the said lamp, the start switch 400 can be released with every assurance thatthe grinding wheel motor will continue to operate.

The next step for the operator is to start the regulating wheel motor 40 which is preferably a direct current motor provided with suitable rectifying means 424 and 426 respectively connecting its series and shunt fields with the 110 volt side of the step-down transformer 410. The regulating wheel motor is energized by closing a biased open regulating wheel start switch 428 connected with a motor relay ZM R in an AC. circuit between the conductors 406 and 408. This circuit also includes a normally closed regulating wheel stop switch 430, and the motor relay 2MR operates to close normally open contacts. 432 which'interlock the stop switch 428 to retainthe energized condition of the said motor relay as indicated by a white lamp 434 connected in parallel with the said motor relay. I 1

The said motor relay 2MR also closes normally open contacts 436 connecting the AC. side of the rectifier 424 with the conductor 406 and normally closed contacts 438, 438 are opened in the parallel circuit to the series field and armature circuit of the regulating wheel motor 40. At the same time, normally open contacts 440, 440 are closed by the motor relay ZMR to complete the connection of the series field and armature of the regulating wheel motor to the DC. side of the rectifier 424. A choke coil 442 and a thermal overload .device 446 are connected in series with the contacts 440, and the said overload operates during a thermal overload to open normally closed contacts 444 in the conductor 408. Therefore, in the event of overload of the regulating wheel motor 4%), the entire electrical system will be deenergized.

Having started the grinding wheel and the regulating wheel, the operator can then start the motor which reciprocates or cycles the regulating Wheel assembly toward and away from the grinding wheel to effect the grinding operation of each workpiece. The regulating wheel cycle or feed motor is also preferably a DC. motor, and it was previously mentioned that this motor is located within the cabinet 36. On the wiring diagram, the cycle motor being indicated generally by the reference number 448, is shown as having rectifying means 450 and 452 connecting its series and shunt fields with the conductors 406 and 408.

The means for starting the cycle feed motor 448 includes a dial type cycle on and cycle off switch 454 located on the control panel. When this switch is placed in the on position it will close and remain in closed position until the operator changes it to the off or open position. The cycle start means also includes a selector type start switch 456 which can be moved to a once position or to a repeat position prior to starting. As will be seen, when the switch 456 is preconditioned by selection of the once position, the regulating wheel 14 will be driven through one cycle "of reciprocation and then stopped, out if the switch 456 is set to repeat, the regulating wheel cycles will be repeated.

Assuming in the first instance that the switch 456 is set to the once position and thereafter closed by pressing its push button, a motor relay SMR connected in circuit therewith between the conductors 406 and 408 will be energized, energization of the said relay being indicated by a green lamp 457. Whenever the motor relay 3MR is energized, normally closed contacts 458 and 460 in parallel with the series field and armature feed cycle motor 448 will be opened and normally open contacts 462, 463 and 464 will be closed in a circuit with the series field and armature of the motor to energize the said motor. The said last mentioned circuit also includes a choke coil 466 and a thermal overload device 468 having normally closed contacts 470 in the conductor 408 and which are opened in the event of overloading the cycle feed motor 448 to deenergize the entire electrical system.

The motor relay 3MR also operates to close normally open contacts 472 in one of a pair of parallel circuits,

said one circuit including normally open switch 474 which is ganged to the switch 456. The other parallel circuit includes a normally closed pole 476 of a two-pole limit switch 477 (FIG. 12). However, the said limit switch is arranged for engagement by the regulating wheel assembly in its fully retracted or initial position so that at the time the motor relay 3MR is initially energized and the contacts 472 are closed, the limit switch pole 476 will be open. Since energizing the motor relay 3MR causes the cycle feed motor 448 to start operation, the regulating wheel assembly will start moving toward the grinding wheel to release the aforesaid limit switch and thereby permit the pole 476 to close.

The other pole 478 of the said limit switch is normally open but it is initially held closed by the regulating wheel assembly in its initial position. 478 is in circuit with a control relay ICR, that relay will energize to close normally open contacts 480 in a direct circuit with the motor relay 3MR. Due to the provision of the control relay ICR having the normally open contacts 480, the start switch 456 can be closed and immediately released with the assurance that the motor relay 3MR will remain energized until the regulating wheelassembly has started movement to effect closing of the limit switch pole 476. A third switch 482 is ganged with the switches 456 and 474 in the circuit to the control relay ICR so that the said control relay will notbe initially energized unless and until the start switch 456 is closed. Further, when the control relay lCR is energized, normally open contacts 484 are closed around the switch 482 to retain the control relay lCR in an energized condition until the pole 478 of the limit switch opens.

Therefore, when placing the cycle selector switch on once and after pressing the cycle start switch 456, the motor relay 3MR will be energized to start operation of the cycle motor 448 which causes the regulating wheel assembly to move from its initial position toward the grinding wheel. After such movement has commenced, the limit switch pole 476 will close to maintain the motor relay energized and to continue the operation of the cycle motor. The cycle motor will continue to operate until the regulating wheel assembly has advanced to the grinding wheel, a grinding operation has been completed and the regulating Wheel assembly has returned to its initial position. At its initial position, the limit switch pole 476 will again be opened to deenergize the motor relay 3MR and thereby to deenergize the cycle motor 448, leaving the regulating wheel assembly at its initial position.

When the cycle operating selector is placed on the repeat position, the switch 474 is closed and remains closed until the selector is removed from the repeat position. Under this circumstance, when the start switch Since the pole s,ose,ees

456 is closed to energize the motor relay 3MR and thereby to close the contracts 472, the motor relay 3MR will remain energized despite opening and closing movements of the limit switch poles 476 and 478. Therefore, the cycle motor 484 will continue steady operation thereby reciprocating or cycling the regulating wheel assembly until the cycle selector switch 454 is opened.

It is an important feature of the present invention to control the speed of the movement of the regulating wheel assembly and the regulating wheel R toward and away from the grinding wheel G. In accord therewith, the control is adapted to provide for rapid feeding or traverse movement of the regulating wheel R toward the grinding wheel G from the initial position of the regulating wheel assembly until the said assembly closely approaches the limit of its advance movement, at which time the workpiece W will be engaged and ground by the grinding wheelG. The control means also provides for relatively slow movement over the final portion of the advance of the regulating wheel toward the grinding wheel during the time the workpiece is ground and sparked out. Thereafter, rapid movement of the regulating wheel assembly is provided to retract it to its initial position.

To this end, the D.C. cycle feed motor 448 is adapted for rapid and slow operation resulting in rapid and slow movement of the regulating wheel assembly, respectively. The control means referredto comprises a normally open limit switch 486'which is connected in series with a timed relay TR. As shown in FIG. 12, the limit switch 486 is arranged to be engaged and closed by the cam 212 which can -be angularly adjustably secured on the regulatting wheel cycle drive shaft 208. By adjusting the position of the cam 212 on the shaft 208, it can be arranged to engage and close the limit switch 486 in any selected advanced position of the regulating wheel assembly. When the limit switch 486 is closed, it energizes the timed relay TR which thereupon closes normally open contacts 488 and 490 and opens normally closed contacts 494 in the wiring of the cycle motor 448. The normally closed contacts 492 are in a conductor extending fromv the motor rectifier 450 to a variac which provides relatively high potential and thus relatively high speed for the cycle motor 448. The normally open contacts 488 and 490 are in a conductor connecting the motor rectifier 450 with a second variac 496 which provides less potential and thus a slower speed for the cycle motor 448. Accordingly, when the limit switch 486 is engaged and closed by the cam 212 to energize the timed relay TR, low speed operation of the cycle motor results and the feeding movement of the regulating wheel assembly is slowed down. This slow feed operation continues for the time at which the relay TR is set, this time being set to provide for a sufiicient period for the final grinding and sparking out of the finished workpiece. Upon completion of the timed period, fast speed operation of the cycle motor 448 is restored and the regulating wheel assembly is retracted rapidly. Obviously, the variable speed traverse will operate either in one cycle or in repeated cycle operation.

The grinding wheel is dressed whenever the operator desires. The dressing operation is started by the operator pressing a normally open push button switch 580 on the control panel. The dresser start switch 500 is included in an AC. circuit between the conductors 406 and 408 with a motor relay MRF which controls operation of the compensator assembly motor 282 to cause forward operation thereof or movement of the rack 286 from left to right as viewed in FIG. 25. There is also included in the said circuit a normally closed dresser stop switch 502 of the push button type and normally closed contacts 504 which are controlled by the relay 3MR so as to be opened and prevent energization of the relay MRF and operation of the compensator motor 282 whenever the relay SMR is energized to etfect cycling or feeding of the regulating wheel assembly. In addition, the circuit to the relay MRF includes normally open contacts 506 which are controlled by the grinding wheel motor relay IMR so as to be closed thereby and assure that the compensator motor will not operate and that wheel dressing cannot be accomplished unless and until the grinding wheel is being driven by the grinding wheel motor 412. Further, the circuit to the relay MRF includes the normally closed pole 508 of the limit switch 3LS (FIG. 25) and normally closed contacts 510 operated by a relay which is subsequently energized as will be described. When the relay MRF is energized, it closes normally open contacts 512 which interlock the dresser starting switch 500 so as to continue dresser and compensator operation after the push button start switch 500 has been released.

As mentioned above, the relay MRF controls and starts operation of the compensator motor 282 which is a reversible AC. motor. More specifically, when the relay MRF is energized as described, it closes a pair of contacts 514 and a pair of contacts 516 connected in series with the compensator motor 282 on opposite sides thereof in a circuit between the conductors 406 and 408. This circuit includes a pair of overload devices 518, 518 which operate a pair of normally closed contacts 520, 520 in the conductor 408 to open them in the event of thermal overload of the compensator motor 282.

As was mentioned, the compensator motor 282 is reversible, and when it is energized by operation of the relay MRF as just described, it operates to move'the rack 286 (FIG. 25) from left to right as shown therein. In movement of the said rack in this one direction, the gear segments 174 and 280 are moved in one direction to engage the ratchets and pawls to rotate their associated shafts in one direction and the regulating wheel assembly 30 and the grinding wheel guard housing 48 carrying the dresser assembly are both moved or adjusted toward the grinding wheel G as has been described. Upon initiation of this right-hand or forward movement of the rack 286, the dog 288 carried thereby disengages the single pole limit switch 2LS permitting the said normally closed limit switch to close in a circuit between the conductors 406 and 408 which includes a motor relay MRR. The circuit to the relay MRR also includes normally closed contacts 522, 522 which are held open while the relay MRF is energized to effect the aforedescribed forward movement of the rack 286.

Therefore, the said forward movement of the said rack will continue until its dog 290 engages the limit switch 3L5 (FIG. 25 at which time it opens the normally closed pole 508 of the said limit switch and closes a normally open pole 524 thereof. When the pole 508 is opened the relay MRF will be deenergized. Upon deenergization of the relay MRF, the normally closed contacts 522 in the circuit with the relay MRR will close to complete that circuit and energize the relay MRR. When the relay MRR is energized normally closed contacts 510 in the circuit to the relay MRF are opened to prevent energization of that relay with the relay MRR. Further, when the relay MRR is energized, normally open contacts 526 are closed to interlock the pole 524 of the limit switch 3L8 thereby maintaining the relay MRR energized until the rack 286 returns to its initial position and opens the limit switch 2LS by means of the dog 288.

Further, when the relay MRR is energized, it closes normally open pairs of contacts 523, 530 and 532 to the compensator motor 282 to again energize it for operation in the opposite direction to reverse the direction of move ment of the rack 286 from right to left as viewed in FIG. 25. The compensator motor 232 will operate in this opposite direction to reverse the rack 286 until it returns to its initial position engaging and opening the limit switch 2L8 which deenergizes the relay MRR and thus deenergizes the compensator motor 282. The compensator 

1. IN A CENTERLESS GRINDING MACHINE OF THE TYPE HAVING A ROTATABLE GRINDING WHEEL AND A REGULATING WHEEL ASSEMBLY ADAPTED TO BE RECIPROCATED TOWARD AND AWAY FROM THE GRINDING WHEEL, MEANS FOR EFFECTING SUCH RECIPROCATION INCLUDING VARIABLE SPEED DRIVE MEANS, A DRIVEN SHAFT OPERATIVELY CONNECTED WITH SAID DRIVE MEANS AND ROTATABLY SUPPORTED IN THE SAID ASSEMBLY AND HAVING AN ECCENTRIC PORTION, A PITMAN PIVOTALLY CONNECTED AT ONE END TO THE ECCENTRIC PORTION OF THE SHAFT, MEANS PIVOTALLY SECURING THE OTHER END OF THE PITMAN TO DEFINE AN INITIAL POSITION FOR THE SAID ASSEMBLY WHEREBY FOR EACH ROTATION OF THE SHAFT THE ASSEMBLY WILL BE RECIPROCATED FROM ITS INITIAL POSITION TOWARD AND AWAY FROM THE GRINDING WHEEL, A CAM SECURED TO SAID SHAFT FOR ROTATION THEREWITH, AND MEANS ENGAGEABLE BY SAID CAM AND OPERABLE THEREBY TO CHANGE THE SPEED OF SAID DRIVE MEANS AND THUS TO ALTER THE RATE OF MOVEMENT OF THE SAID ASSEMBLY DURING EACH RECIPROCATION THEREOF.
 8. A CENTERLESS GRINDER HAVING A GRINDING WHEEL ROTATABLE ON A LONGITUDINAL AXIS, A GRINDING WHEEL DRESSER ASSEMBLY MOVABLE TRANSVERSELY TOWARD THE GRINDING WHEEL FROM ONE SIDE OF ITS AXIS TO EFFECT A DRESSING OF THE GRINDING WHEEL, A REGULATING WHEEL ASSEMBLY INCLUDING A ROTATABLE REGULATING WHEEL AND WHICH IS MOVABLE TRANSVERSELY TOWARD THE GRINDING WHEEL FROM THE OTHER SIDE OF ITS AXIS TO MAINTAIN A DESIRED SPACED RELATIONSHIP THEREWITH FOR GRINDING OPERATIONS, MEANS FOR MOVING EACH OF SAID ASSEMBLIES EACH OF WHICH MEANS INCLUDES A ROTATABLE SHAFT HAVING A GEAR ROTATABLY MOUNTED THEREON AND HAVING MEANS EFFECTING A DRIVING CONNECTION TO CAUSE SIMILAR ROTATION OF THE SHAFT WHEN ITS GEAR IS ROTATED IN ONE DIRECTION, A RACK ENGAGING BOTH OF SAID GEARS, AND DRIVE MEANS FOR RECIPROCATING SAID RACK WHEREBY TO MOVE BOTH OF SAID ASSEMBLIES TOWARD SAID GRINDING WHEEL DURING EACH RECIPROCATION OF SAID RACK TO RESPECTIVELY DRESS THE GRINDING WHEEL AND RE-POSITION THE REGULATING WHEEL ASSEMBLY TO COMPENSATE FOR THE REDUCED DIAMETER OF THE DRESSED WHEEL. 